In enzymology, a myosin light-chain phosphatase (MLCP) is an enzyme

Enzyme

Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 that catalyzes

Catalysis

Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....

 the chemical reaction

Chemical reaction

A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...

[myosin light-chain] phosphate + H₂O [myosin light-chain] + phosphate

Thus, the two substrates

Substrate (biochemistry)

In biochemistry, a substrate is a molecule upon which an enzyme acts. Enzymes catalyze chemical reactions involving the substrate. In the case of a single substrate, the substrate binds with the enzyme active site, and an enzyme-substrate complex is formed. The substrate is transformed into one or...

 of this enzyme are myosin light-chain phosphate and H₂O

Water

Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

, whereas its two products

Product (chemistry)

Product are formed during chemical reactions as reagents are consumed. Products have lower energy than the reagents and are produced during the reaction according to the second law of thermodynamics. The released energy comes from changes in chemical bonds between atoms in reagent molecules and...

 are myosin light-chain and phosphate

Phosphate

A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...

.

This enzyme belongs to the family of hydrolase

Hydrolase

In biochemistry, a hydrolase is an enzyme that catalyzes the hydrolysis of a chemical bond. For example, an enzyme that catalyzed the following reaction is a hydrolase:-Nomenclature:...

s, specifically those acting on phosphoric monoester

Ester

Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...

 bonds. The systematic name of this enzyme class is [myosin-light-chain]-phosphate phosphohydrolase. Other names in common use include myosin light chain kinase phosphatase, myosin phosphatase, myosin phosphatase, protein phosphatase 2A, and myosin-light-chain-phosphatase.

Structural studies

MLCP is composed of three subunits: a PP1c

PPP1CB

Serine/threonine-protein phosphatase PP1-beta catalytic subunit is an enzyme that in humans is encoded by the PPP1CB gene.-Interactions:PPP1CB has been shown to interact with PPP1R15A, Nucleolin, SMARCB1 and PPP1R9B.-Further reading:...

 catalytic subunit, a myosin targeting subunit called MYPT1

PPP1R12A

Protein phosphatase 1 regulatory subunit 12A is an enzyme that in humans is encoded by the PPP1R12A gene.-Interactions:PPP1R12A has been shown to interact with Interleukin 16.-External links:* Info with links in the...

, and a small subunit of unknown function called M20.

As of late 2007, only one structure

Tertiary structure

In biochemistry and molecular biology, the tertiary structure of a protein or any other macromolecule is its three-dimensional structure, as defined by the atomic coordinates.-Relationship to primary structure:...

 has been solved for this class of enzymes, with the PDB

Protein Data Bank

The Protein Data Bank is a repository for the 3-D structural data of large biological molecules, such as proteins and nucleic acids....

 accession code .

Function

MLCP is important for regulating contraction in smooth muscle, which lacks the troponin binding system. It inhibits contraction by dephosphorylating myosin light-chain fibers. It counters the myosin light-chain kinase

Myosin light-chain kinase

Myosin light-chain kinase also known as MYLK or MLCK is a serine/threonine-specific protein kinase that phosphorylates the regulatory light chain of myosin II.- Isoforms :Four different MLCK isoforms exist:* MYLK – smooth muscle...

 (MLCK), which promotes contraction by phosphorylating myosin light-chain proteins. MLCP is present in smaller amounts compared with MLCK, but compensates for this lack of mass by rapid movement along actin fibers. MLCP activity is inhibited by Rhoa

RHOA

Ras homolog gene family, member A is a small GTPase protein known to regulate the actin cytoskeleton in the formation of stress fibers. In humans, it is encoded by the gene RHOA....

 and Rho kinase, components of the Ca²⁺ independent pathway for maintaining muscle contraction.